From German Patent document number 43 28 465, a method is known for manufacturing epoxysiloxane condensates in which epoxysiloxanes are obtained by condensation of epoxy-functional alkoxysiloxanes with silanoles. These epoxysiloxane condensates can be used either directly as casting resins or for mixing with epoxy resins for electronics applications. The casting resin systems with epoxy-containing siloxanes are also suitable for the manufacture of temperature-stable and thermomechanically loadable molding materials. The epoxysiloxane condensates have a general structure that can be derived from the epoxyalkoxysilanes used and the silanoles used and chemical analyses. In order further to adapt the epoxysiloxane condensates to the specific areas of use, it is desirable to be able to vary the electronic and steric ratios and also the polarity of the resins within wide limits. By means of the chemical modification of the condensates, custom-tailored casting resins are made available that can be adapted in a particularly flexible fashion to the technical requirements in processing and later operation.